Mounting Low Profile Tyres

Mounting new tyres
Bead Breaking
The demounting
General info about mounting heads
Conclusion

As tyres are getting larger and larger and the sidewall height is getting lower and lower, it is necessary to have a closer look at the increasing difficulties in their mounting, especially in their demounting.

Already when mounting new low profile tyres, care and caution are required in general. Mounting this kind of new tyre, it is more often necessary to rotate the tyre on the rim in order to reduce the use of wheel weights when balancing, than it is for the usual tyre sizes (matching, minimizing, optimizing). To rotate the tyre on the rim, the bead has to be broken several times.

The problem of mounting and demounting low profile tyres is the risk of damaging the tyre and/or the rim which becomes higher and higher the stiffer and lower the sidewall. The zone between bead and shoulder is so small that there is no more a flexible sidewall left.

Suggestions and hints are given on the following subjects regarding the mounting and demounting of modern low profile tyres:

1. Mounting new tyres
   
2. Bead breaking
   
3. Demounting
   
4. General information about mounting heads

There are not real difficulties in mounting modern low profile tyres when mounting cream is properly applied to rim and bead and the hints here below are followed.

This presupposes, however, that rims with a reserved drop center (drop center at the inside of the rim) are clamped accordingly on the tyre changer. In quite a number of cases, a clear indication under the form of a sticker can be found in the area of the wheel disk. Rims with an offset drop center have to be clamped with their car - outside facing downwards on the tyre changer.

For clamping a wheel on the tyre changer, we recommend if possible, a blocking from the inside (not on the rim edge) in order to avoid the jaws damaging the rim edge. If there is no tyre changer available for inner clamping, protectors have to be put on the metal jaws to prevent rim edge damage.

Such protectors are supplied as accessories by various manufacturers and distributors of workshop equipment. If such protectors are not available, a piece of rubber, leather or similar material can be put between jaw and rim shoulder.

The use of a bead pusher facilitates the mounting of the more difficult second head. This is avoiding the help of a second person trying to push and to keep the bead in the drop center. The bead pusher allows the tyre to be mounted by one person, whereas two persons were necessary in the past. However, the use of a bead pusher is not quite problem - free either. Excessive pressure on it may lead to rim damage and pressure marks on the clamped rim edge.

Further important hints regarding mounting heads can be found under the chapter “General info about mounting heads.”

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Before bead breaking, the valve core has to be removed in all cases, to allow a complete deflation of the tyre.

Bead breaking above the rim protection (not recommended)

The risks caused by bead breaking with the bead breaker positioned between shoulder and rim protector (= sidewall, which is the weakest part of the tyre) are the following:

• risk of sidewall damage caused by excessive elongation of the carcass wires or even breakage of the carcass
• a distorted bead (the bead jams and gets into the drop center with extreme difficulty)
• permanent deformation of the steel cord at the belt sides
• deteriorating eccentricity, especially force oscillations

The permanent deformation as shown on the photograph, which extends into the shoulder, is caused by distortion of the bead. This distortion arises from the fact that the bead lip is held by the hump whereas the sidewall is being pressed in. As the sidewall is already strongly pressed inwards, before the already strongly distorted bead slams into the drop center, this deformation is inevitable.

Due to this considerable permanent deformation of the steel cord, it cannot be excluded that the lateral and radial force oscillations as well as the uniformity of the tyre are adversely affected to a large extent. In view of such deformations, any liability has to be excluded in case of complaints about eccentricity or oscillations.

The soft and instable sidewall is damaged by the pressure of the bead breaker blade which is too strong for this area of the tyre. The bead area however, which is stiff, bears this pressure far better.

To avoid the above mentioned problems, it is extremely important to position the bead breaker blade as near as possible to the rim edge.

Bead breaking between rim edge and the tyre's rim protector (recommended method)

The rim edge can be scratched by the bead breaker blade if handled without taking care. This can be avoided by working cautiously and carefully.

When positioning the bead breaker blade, pay attention to its curvature, which must be appropriate to the respective rim diameter. A bead breaker blade designed for 13” rims cannot fit perfectly a 17” rim in such a way that it provides an optimum force distribution in the bead breaker area. For this purpose, modified bead breaker blades with an appropriate radius of curvature are available at distributors of workshop equipment. It is clear that such tools are helping to avoid rim and tyre damage.

Solutions for the above-mentioned problems

After an appropriate bead breaker blade has been positioned, the head can be loosened a little bit by pressing briefly against the upper sidewall (don't push through).

Having done this, the bead becomes much easier to break and to push into the drop center with the bead breaker blade positioned correctly between rim edge and rim protector, without any risk of scratching the rim edge.

However, the danger of an excessive deformation of the shoulder and the cord belt, remains.

The solution to this problem is brought by a new mounting machine, which breaks both beads at the same time, under rotation of the already clamped wheel, using two nylon rollers. They cause little or no deformation at all. Another advantage for the operator is the fact that there is no need anymore to put the wheel on the floor for bead breaking.

This is a time saving procedure as the wheel remains in this position after the bead breaking to demount the old and to mount a new tyre on the rim.

The clamped wheel, under rotation, is undergoing the bead breaking of both beads at the same time without any risk of being damaged.

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To pull the tyre out of the rim with a lever

The demounting, on the contrary to the mounting, may cause much larger problems which can be avoided, knowing the details to take into consideration.

Considering a normally clamped rim (the drop center is at the upper side), the bead has to be held into the drop center at the 6 o'clock position by hand, and if this is not possible, it can be managed using a couple of bead levers.

The mounting head represents the 12 o' clock position.

By the help of these, into the drop center pointed levers, the operator assures that the bead remains in the drop center while at the 12 o'clock position the bead gets lifted on the demounting tool, paying attention that the lever point is not puncturing the sidewall under the pressure exerted by the bead tension.

An excellent helping-device for carrying out such an operation is the plastic lever protector (Tip Top ref. no. 5198041). This device allows the lever to slide out of the tyre more easily and reduces the risk of rim damage when the lever slips from the mounting head.

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The traditional mounting head:

On a traditional tyre changer, when a strong mounting force is expected, it is usual to increase the standard 3 mm distance of the mounting head which is set by the automatic locking device (if available). If this distance is not increased, and working with a tightly fitting tyre, it is easily possible that during mounting and demounting under the enormous bead tension, the mounting head gets pulled against the rim edge causing an immediate damage or even worse, scrapes away metal from the same edge. This type of damages can cause a considerable acceleration of the corrosion on the bare aluminum and quickly lead to the destruction of the rim. It's easy to imagine what type of problems lead to such a mistake.

Worn out mounting heads may cause bead damages.

During the mounting of the last bead section, where the bead is under extreme tension before slipping into the rim, the sharp edge of a worn out mounting head can cut the bead and/or the bead lip.

This sharp points under the mounting head can have been caused by not removing wheel weights from the rim edge. Damage of this type is generally discovered at an advanced stage. Therefore, it is important to emphasize again the removal of all wheel weights from the rim edges prior to clamping the rim on the tyre changer. Further, also periodical controls of the mounting head can avoid this type of damage.

New type of mounting head

Since some time, a completely new conceived tyre changer is available on the market (in use at the Uniroyal Customer Service), having a newly engineered synthetic mounting head which allows a completely damage free operation on rim and tyre. Since May 1992, this unit is available in an advanced version able to handle all modern passenger car tyres of any diameter or width.

On machines with a separate mounting head adjustment, it has to be clear that the distance between mounting head and rim edge should not be too large in order to avoid that the bead gets stressed during mounting which can result easily in a bad bead seating.

Due to an overstressed bead during demounting, the re-use of such a tyre can be seriously questioned. The seating of the bead isn't perfect anymore and the bead was exposed to a deformation in the zone where the lever was positioned.

When the pressure of the bead on the lever is too high, the lever cannot automatically slide out of the tyre once the bead is brought on the mounting head. In this case, the pointed end of the lever can puncture the sidewall or the shoulder of the tyre, damaging it in an irreparable way.

The new mounting head, made of a synthetic material, allows a damage free operation on the rim edge. All metal parts have been eliminated for this reason.

An important improvement in comparison with the older version is a new bead breaker device with two big plastic rollers which break the upper and the lower bead at the same time during the rotation of the already clamped wheel. This time saving detail has already been described. Further advantages of this unit is the fact that the bead breaker functions as a help during the mounting as well as during the demounting. Further, due to its configuration, matching, optimizing and minimizing become extremely simple and damage free.

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Mounting of new tyres

• greasing tyre and rim
• clamp the rim with the drop center up on the tyre changer
• apply the jaw protections when clamping a light alloy rim from outside
• pay attention to possible rim damage caused by the bead pusher

Bead breaking

• remove the valve core to allow the tyre to deflate
• don't position the blade in the sidewall (exception: pre-press)
• break the bead as close as possible to the rim edge
• avoid rim damage
• pay attention to the radius of the blade

Demounting

• before demounting remove all the wheel weights
• keep the tyre in the drop center at the 6 o'clock position, using a bead lever
• protect the bead lever with a plastic protector shoe

General info on mounting heads

• attention to the right mounting head adjustment
• too much stress during demounting means a wrong mounting head adjustment and an overelongation of the bead
• control the mounting head on damage

Tyre changers using the latest technology are resolving almost all existing mounting problems.

With these detailed instructions for (de)mounting, it should be possible to approach these 17”-18” rim-tyre combinations with less fear.

©1993 by UNIROYAL ENGLEBERT All rights reserved.

Reproduction, reprint, or any other form of duplication – even as excerpts – is only permitted with other authorization from UNIROYAL ENGLEBERT.

Reprinted by permission of UNIROYAL ENGLEBERT

The contents of this manual were compiled with the greatest care and reflect decades of experience. To the best of our knowledge all data and tips are correct but they do not guarantee any features. It should be remembered that by the time this manual is in use, certain specifications may be out-of-date, mainly as a result of technical progress. No liability for damage of any kind or for any legal reason can be accepted for advice given in this manual.

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Form 3848T, 2-95